Decorated Cyclopentadienes from Acetylene and Ketones in Just Two Steps

The products of the one-pot assembly of acetylene and ketones in the KOH/DMSO system, 7-methylene-6,8-dioxa­bicyclo­[3.2.1]­octanes, undergo an acid-catalyzed (CF₃COOH, room temperature) rearrangement to rarely substituted cyclopenta­dienes in good-to-excellent yields. The mechanism of the rearrangement has been supported by the isolation and corresponding transformations of two intermediates

A One-Pot Synthesis of 2‑Aminopyrimidines from Ketones, Arylacetylenes, and Guanidine

The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBu^<i>t</i>/DMSO system leads to 2-aminopyrimidines in up to 80% yield. Depending on structure of the starting ketones, the aromatization of intermediate dihydropyrimidines occurs either with loss of hydrogen molecules or methylbenzenes. The latter process takes place in the ketones, in which one of the substituents is not a methyl group. The reaction conditions are tolerable for dialkyl-, aryl­(hetaryl) alkyl-, and cycloalkyl ketones

Transition-Metal-Free, Atom- and Step-Economic Synthesis of Aminoketopyrrolizines from Benzylamine, Acylethynylpyrroles, and Acylacetylenes

A concise, atom-economic strategy for the synthesis of pyrrolizines with amino and keto substituents has been developed. It includes the following key steps: (i) the base-catalyzed (K₃PO₄/DMSO) addition of a benzylamine to 2-acylethynylpyrroles and (ii) noncatalyzed addition of enaminones obtained to the triple bond of acylacetylenes followed by intramolecular cyclization of the intermediate pentadiendiones thus formed to the target 1-(benzylamino)-2-acyl-3-methylenoacylpyrrolizines

An Expedient Access into Functionalized Furan/3(2<i>H</i>)-furanone Ensembles via Microwave-Assisted Domino Reactions

<div><p></p><p>A one-pot linkage between furan and 3(2H)-furanone rings has been effected via the microwave-assisted Et₃N-catalyzed domino condensation of the furan and benzofuran carboxylic acids with available cyanopropargylic alcohols (MeCN, 100 °C, 1.2 atm, 2-17 h). Despite involving a number of C-H-forming/breaking steps, the assembly is chemoselective and the final products, 5-(2-furyl)-3(2H)-furanones, are formed in 59-96% yields.</p></div

A One-Pot Approach to Δ²‑Isoxazolines from Ketones and Arylacetylenes

The sequential reaction of ketones with arylacetylenes and hydroxylamine in the presence of KOBu^<i>t</i>/DMSO followed by the treatment of the reaction mixture with H₂O and KOH leads to Δ²-isoxazolines in up to 88% yield

Exploring Acetylene Chemistry: A Transition Metal-Free Route to Dienyl 6,8-Dioxabicyclo[3.2.1]octanes from Ketones and Acetylenes

Dienyl derivatives of 6,8-dioxabicyclo[3.2.1]­octanes, closely related to naturally abundant molecules, have been synthesized from 2-acetyl-3,4-dihydropyrans (readily available from ketones and acetylene in two steps), which further add to aryl­(hetaryl)­acetylenes in the KOBu^t/DMSO superbase system (105 °C, 1.5 h) to stereoselectively give the corresponding <i>E</i>-styryl adducts. The latter undergo ring closure (NH₄Cl/H₂O, acetonitrile, reflux, 8 h) to form the 6,8-dioxabicyclo[3.2.1]­octane core decorated with the (1<i>Z</i>,3<i>E</i>)-diene substituent

Base-Catalyzed Domino Cyclization of Acetylenes with Ketones to Functionalized Cyclopentenes

Acetylene reacts with methylaryl­(hetaryl)­ketones in the presence of 6.5 mol % KOH in DMSO to give diastereoselectively in single operationally functionalized cyclopentenes. This domino cyclization involving two molecules of acetylene and two molecules of ketone proceeds with the formation of four C–C bonds. The complementary assembly of the cyclopentenes with similar functionalities from acetylenes and 1,5-diketones has been developed

Synthesis of Acyl Terphenyls and Higher Polyaromatics via Base-Promoted C–H Functionalization of Acetylarenes with Arylacetylenes

KO<i>^t</i>Bu/DMSO-promoted C–H functionalization of acetylarenes with arylacetylenes (100 °C, 30 min), generating β,γ-ethylenic ketones, triggers upon further heating (100 °C, 4 h, with or without acidifying additive) the cascade assembly of acyl terphenyls and higher polyaromatics in good yields